Endoscopic instruments with a flexible or rigid instrument shaft are used both in industry and also in medicine. For example, flexible endoscopes are used in veterinary medicine for gastro-endoscopic examination of large animals. These endoscopes often have, at a distal end of their instrument shaft, a distal end portion, which finishes in an endpiece. The endpiece represents the distal part of the endoscope that is inserted into the body to be examined. It usually has the distal end of an endoscope lens system and also some of the suction, flushing and instrument channels.
To be able to ensure the greatest possible flexibility as regards a spatial orientation of the endpiece during the examination, the end portion of the instrument shaft is usually configured to be deflectable. By a deflection, or general actuation, of the portion relative to the rest of the instrument shaft, in particular by bending or curving, a part of the instrument shaft, in particular the endpiece, can be given the desired orientation. During this deflection, a user has to proceed carefully in order to ensure that no damage is done to any tissue located around the end portion. It is therefore important that the actuation of the portion can be very precisely controlled.
In flexible and rigid endoscopes according to the prior art, the portion is deflected via a pull element, in particular via Bowden cables. The pull element is connected to an adjustment element, in particular a steering gear. The pull element is often secured on a cord pulley. By actuation of the control element on the control section of the endoscope, the adjustment element is moved. A rotary movement of the adjustment element results in a translational movement of the pull element. The movement of the pull element in turn results in a deflection of the portion.
U.S. Pat. No. 4,499,895 relates to an electrical endoscope, which is controlled via a lever coupled to the adjustment element. When the lever is moved relative to the adjustment element, a flexion of the lever or a change in resistance of a potentiometer is detected and, in this way, the adjustment element is assisted by an actuator. However, the construction shown is very unwieldy and, in the event of a fault, requires a special release mechanism in order to be able to continue operating the endoscope.
U.S. Pat. No. 7,331,924 relates to an electrical endoscope with a deflectable distal portion. The endoscope is controlled in this case using a track ball, of which the movement caused by the thumb or another finger of a user is detected by an electrical circuit. Depending on the rotary movement of the track ball, as chosen by the user, a deflection control system triggers a motor, which causes a movement of the pull element and therefore a deflection of the distal portion.
However, the disadvantage of an electrical endoscope of this kind is that the control feels less intuitive, since the control of an electrical endoscope, e.g. when the latter strikes against tissue, does not provide the kind of feedback, in the form of a counterforce on the control element, that a person receives when using mechanical endoscopes. These problems are also found in electrical endoscopes that are controlled using a joystick. In this connection, reference is made purely by way of example to the document U.S. Pat. No. 6,932,761. Electrical endoscopes also have the disadvantage that, in the event of a defect, it is difficult to withdraw them from the cavity when the distal portion has been deflected.
In mechanical endoscopes, the portion is deflected exclusively by a mechanical force applied by the user to an external handle on the control section of the endoscope. For this purpose, the adjustment element is usually arranged fixedly on a shaft of the handle. When the user actuates the handle, this causes a rotary movement of the adjustment element and therefore in turn the translational movement of the pull element.
However, depending on the endoscope length and on the position of the instrument shaft, purely mechanical endoscopes may require considerable forces for actuating them. Moreover, the mechanical actuation of the portion automatically generates a certain restoring force in the direction of the non-deflected position (zero position) of the endoscope. Furthermore, during the deflection, the portion forms, together with the pull element, a spring/damper system which stores energy when tensioned and releases energy when relaxed. This can result in a start-up idle time or a slow-down in the deflection of the end portion. The effect of this is that, as regards the deflection he would like to confer on the portion in order to be able to view a certain location, the user can obtain this only approximately or iteratively.